In manufacturing a semiconductor device, there is a process of forming a silicon-based insulating film such as a silicon nitride film (SiN film), i.e., an insulating film containing silicon as a predetermined element, on a substrate such as a silicon wafer. Since the SiN film has good insulating properties, corrosion resistance, dielectric properties, film stress controllability, and the like, it has been widely used as an insulating film, a mask film, a charge accumulation film, or a stress control film. Also, a technique of forming a silicon carbonitride film (SiCN film) by adding carbon (C) to the insulating film for the purpose of improving etching resistance has been used.